4. Click on the "No Throttling" dropdown and check "Offline".
5. You should now see a yellow warning icon in your Network tab and it should prevent all network access. If you reload the tab you should get the "No Internet Connection" error page.
I've long been wishing for the same! With service workers etc. this would be a perfect approach for many small utilities. I've started building things as single HTML files using vite-plugin-singlefile[0], but users either have to manually block network requests, or they have to trust me. It would be awesome if they could be sure that nothing will be uploaded anywhere.
The pledge would have to be persistent, which would make e.g. service worker updates difficult - ideally the browser should show you that an update is available, and offer to delete all stored information so nothing can be saved to localStorage etc. to be uploaded afterwards.
AFAICT it's purely frontend, there is no uploading. Aside from running it yourself, another thing you can do is go into devtools and set the network throttling to "offline". (Note that this is not fool-proof, but it does prevent new connections from being established.)
It's hard to know whether anything is actually uploaded, but thankfully SQLite databases are plentiful that don't contain sensitive data (and this, also, is why there is a sample database included).
1. Permanently restrict the browser tab from accessing the network.
2. Show an indication of this in the browser UI outside of the content area.
It would be perfect for this kind of app.